The present invention relates to a ring laser gyroscope, and more particularly to an improved optical configuration in the ring laser gyroscope employing an offset aperture.
Ring laser gyroscope (RLG) devices for measuring angular rotation rates area known in the art. In these devices, two laser beams are generated in opposite directions around a closed loop path about the axis of rotation of the device. Rotation of the apparatus causes the effective path length for the two beams to change, thus producing a frequency difference between the two beams since the frequency of oscillation of the laser beams is dependent upon the length of the lasing path. The frequency difference between the beams causes a phase shift between the beams that changes at a rate proportional to the frequency difference. The interaction of the beams produces an interference fringe pattern which is observed to move with a velocity proportional to the rate of angular rotation of the device about the axis.
In the closed loop optical path of laser propagation, it is necessary to provide an aperture having a size that is sufficiently small so that the 10 laser mode (having two dots side-by-side) and the 01 laser mode (having two dots in a vertical stack) have significant losses from passing through the aperture and therefore do not oscillate and affect the frequency of the 00 laser mode (having a single centered dot). However, as the size of the aperture is reduced, the mirrors in the optical laser path must be more precisely positioned to enable proper operation of the device, which is a time and labor intensive process and therefore increases the total cost of the RLG. Therefore, previous RLG devices have been designed with this trade-off taken into account. It would be an improvement to the current state of the art to provide an RLG having an aperture design that reduces the precision necessary in mirror positioning without having an adverse effect on the optical performance of the device.
The present invention is a ring laser gyroscope (RLG) employing an offset aperture for attenuating undesired modes of laser propagation therein. The RLG includes a block having a ring laser cavity containing a lasing gas, the cavity being substantially in the shape of a polygon having at least three sides and at least three vertices formed by the intersection of sides of the polygonal cavity. At least three mirrors are provided, equal in number to the number of vertices and positioned at the vertices to create a resonant ring laser having a polygonal ring path in the shape of the polygon. At least one aperture is provided in the ring laser cavity for attenuating undesired modes of laser propagation in the polygonal ring path of the laser. The aperture has an axis that is horizontally offset from a central axis of the polygonal ring path of the laser.